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K20 USB-FS device behavior when the host does not ACK

Question asked by lasseh on Nov 5, 2014
Latest reply on Nov 6, 2014 by Mark Butcher

How does the USB-FS module, configured as a USB device, behave in case that host does not anwer ACK device's response to an interrupt endpoint IN token? This happens if data sent by the device got corrupted, or if the host was not ready for it.

-Does the USB-FS automatically continue trying to resend the same data on subsequent IN token receives? (Until receiving ACK, software crash, or power off...)

-Is observing USBx_ERRSTAT register bit BTOERR (bus turnaround timeout error) the mechanism to recognize this situation?

 

The reference manual does not seem to specify USB-FS behaviour in this situation, but the USB specification suggests something like this.

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